Hydrostatic bearing made of magnetic material which is also used as a motor magnet

ABSTRACT

A permanent magnet motor is provided with a housing, a rotating shaft supported within the housing, and magnetic coils arranged within the housing. A hydrostatic bearing is disposed on the rotating shaft, the hydrostatic bearing having a permanent magnet incorporated therewith that restricts movement of the rotating shaft in a radial direction.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional PatentApplication No. 61/149,794, filed Feb. 4, 2009, which is incorporated byreference as if fully set forth.

FIELD OF INVENTION

This application is generally related to motors or generators havingmagnetic elements, and more particularly related to hydrostatic bearingsconstructed with a permanent magnet that can be used as the permanentmagnetic element of motors or generators.

BACKGROUND

Some motors are designed to use coils in order to generate a magneticfield. These motors include two sets of coils, one located in the statorand one located in the rotor. One set of coils is energized usingconductive contacts or brushes that may touch on the shaft or the movingbody. The current fed to these coils creates an electromagnetic field.Other motors and generators employ permanent magnets to provide motion.Electricity is produced when coils of copper windings are moved relativeto the flux fields generated by the magnets. Alternatively, electricitymay be fed into the coils to produce motion. In both of these scenarios,separate bearings are used to define the relative motion between thecoils and magnets, which may be linear or rotary in nature. In eithercase, the flux field creates an attractive force that must be resistedby the bearings. This force is mitigated in some degree when there is anopposing force applied at 180° from other magnets. Although the opposingforce mitigates the flux field's attractive force, it is not astabilizing force. For example, as the coils get closer to the magnetson one side, the attractive force from those magnets increase, whichmoves the coils further away from the magnets that are arranged at 180°and decreases the applied opposing force. In the absence of separatebearings, the coils and magnets would come into contact and disable themotor or generator's function.

Permanent magnet motors employ magnets made of, for example and withoutlimitation, neodymium NdFeB or ferrite. There are multiple methods formanufacturing these magnets, such as through casting in a mold,pressing, injection molding, or bonding. In most cases, these magnetsare porous, which is especially true for magnets that are sintered.These magnets may be magnetized after they have been formed into theirdesired shape. Motors and generators may employ a wide variety ofmagnetic circuit designs. Permanent magnets may be used on the outsidediameter of a rotating body or on the interior of a housing. They mayuse switched reluctance or induction and may use AC or DC current.

Motors and generators' efficiency and power can be increased byminimizing the distance between the coils in the magnets. As thedistance between the coils decreases, the flux field force increases.However, due to the unstable relationship between the coils and magnetsas described above, relatively large gaps between coils must be used inthe manufacture of motors and generators. Such an arrangement is shownby U.S. Pat. No. 5,036,235 to Klecker.

Design engineers have been trying to achieve more functionality in lessspace. The paradigm today in the design of motors and generators is tohave separate bearings and motor functions. This results in assembliesthat are longer, larger in diameter, and heavier than if the motor andbearing elements can be one in the same. For example, see the assemblyshown by U.S. Pat. No. 5,443,413 to Pflager et al.

In U.S. Pat. No. 5,098,203 to Henderson, magnets are inserted into theface of a hydrostatic bearing assembly in order to increase thestiffness of the hydrostatic film with the magnets' preload force.However, there is no disclosure of using such magnets in a motor orgenerator.

One of ordinary skill in the art of hydrostatic bearings wouldappreciate that air and other gases are examples of a fluid used inhydrostatic bearings. This means that the broad term of hydrostaticbearings encompasses aerostatic bearings, as discussed in U.S. Pat. No.5,488,771 to Devitt et al. The terms “hydrostatic bearings” and“hydrodynamic bearings” are both encompassed in the definition of “fluidfilm bearings.” Hydrostatic bearings are differentiated fromhydrodynamic bearings by the use of an external pressure source, whichallows hydrostatic bearings to operate even with zero velocity betweenthe relative bearing faces. In contrast, hydrodynamic bearings requirerelative motion between bearing faces to create fluid film pressure. Oneof ordinarily skill in the art would also appreciate that hydrostaticbearings exhibit hydrodynamic effects when there is relative motionbetween the bearing faces. These hydrodynamic effects are an unavoidableresult of the shear of the hydrostatic fluid caused by the relativemotion of the bearing surfaces, and are included in the operation ofhydrostatic bearings.

Accordingly, it is an object of the present application to combine thebearing and motor functionalities, provide economy of space, and improveefficiency by reducing the gap in the flux field to the thickness of thehydrostatic bearing fluid.

SUMMARY

A permanent magnet motor is disclosed, the permanent magnet motor havinga housing, a rotating shaft supported within the housing, and magneticcoils arranged within the housing. A hydrostatic bearing is disposed onthe rotating shaft, the hydrostatic bearing having a permanent magnetincorporated therewith that restricts movement of the rotating shaft ina radial direction.

A method for making a permanent magnet motor is also disclosed. Themethod includes the steps of providing a housing with a rotating shaftsupported therein, arranging magnetic coils within the housing, anddisposing a hydrostatic bearing on the rotating shaft. The hydrostaticbearing has a permanent magnet incorporated therewith that restrictsmovement of the rotating shaft in a radial direction. For sake ofbrevity, this summary does not list all aspects of the present device,which is described in further detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a prior art motor having separatebearing and motor components;

FIG. 2 is a cross-sectional view of an embodiment of the hydrostaticbearing of the current invention, which utilizes porous magneticmaterial as the restrictor for the hydrostatic bearing; and

FIG. 3 is a cross-sectional view of another hydrostatic bearing thatserves as the permanent magnet in a motor.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Certain terminology is used in the following description for convenienceonly and is not limiting. The words “inner,” “outer,” “top,” and“bottom” designate directions in the drawings to which reference ismade. The terminology includes the words specifically noted above,derivatives thereof, and words of similar import.

FIG. 1 shows a prior art permanent magnet motor having a rotatable shaft100 supported relative to a housing or stator 105 by a set of bearings103 at each end of the rotatable shaft 100. The bearings 103 may beformed as plain, rolling, fluid film, or magnetic bearings, or any otherform well known to those of ordinarily skill in the art of bearings. Inthis case, the bearings 103 provide both radial and axial constraint.The bearings 103 provide radial constraint by having an outer diameterthat corresponds to the inner diameter of the housing or stator 105, andprovide axial constraint by being disposed between a shoulder 100a ofthe rotatable shaft 100 and a stationary retaining cap 106 of thehousing or stator 105. Accordingly, the bearings 103 substantiallyconstrains five degrees of freedom of the rotatable shaft 100, leavingonly rotation unrestrained.

The prior art motor's motor elements are completely separate from thepermanent magnets. Coils 101 are wrapped by 360° around the innerdiameter of the housing or stator 105. Magnets 102 are disposed aroundthe outer diameter of the rotatable shaft 100, leaving an air gap 104between the magnets 102 and coils 101. The air gap 104 must be largeenough to accommodate error motions in the bearings 103, out of balancecentrifugal forces, and centrifugal force growth of the magnets 102 androtor.

FIG. 2 shows an embodiment of a hydrostatic bearing according to thepresent invention. A magnetic material 200 that can be acted upon by anattractive magnetic field from a porous magnet 201 is separated from theporous magnet 201 by a pressurized hydrostatic film 206. The hydrostaticfilm pressure is maintained by a continuous flow of fluid, which ispumped through the porous magnet 201 by a pressure higher than ambientpressure. This pressurized fluid is introduced through input ports 202and distributed across a back surface of the porous magnet 201 by alabyrinth 204. As shown in FIG. 2, the labyrinth 204 may be formed in anon-porous housing 203. In an alternative embodiment, which is notillustrated by the drawings, the labyrinth 204 may be formed in theporous magnet 201 itself. In a further alternative embodiment, also notillustrated by the drawings, the labyrinth may be formed in a separatemodular bearing component that is mounted inside of the non-poroushousing 203 or to a separate structure using a mounting stud 205, whichmay be attached through a flexure, gimbal mount, bolted joint, or bondedin place as disclosed in U.S. Pat. No. 5,488,771 to Devitt et al. In theabove embodiments, the non-porous housing 203 and the porous magnet 201are laminated together by any suitable means, such as through gluing,glazing, or grazing operations. These methods are well known in the artof manufacturing porous media hydrostatic bearings and have beendescribed in U.S. Pat. No. 6,515,288 to Ryding et al. The pressurizedfluid is also useful for removing heat from the bearing surfaces of thehydrostatic bearing and from the hydrostatic gap.

FIG. 3 shows a preferred embodiment of a hydrostatic bearing accordingto the present invention utilized in a permanent magnet motor. Arotating shaft 300 is provided with porous permanent magnet components302 laminated onto the outer diameter of the rotating shaft 300. Alabyrinth 312 is provided behind the porous magnet components 302 in asimilar manner as described above with respect to FIG. 2. In order tosupply the labyrinth 312 with a pressurized hydrostatic fluid, the fluidcan be ported through a hole 309 in each retaining cap 306 on eitherside of the housing 305 and distributed through a groove 310 in theretaining caps' inner diameter that functions as a rotary union due tothe small clearance 307 between the retaining caps 306 and rotatingshaft 300, and finally into a hole 311 in the rotating shaft 300. Thispressurized hydrostatic fluid then issues from the face of the porousmagnet components 302, creating a pressurized film 304 that separatesthe porous magnet components 302 from the magnetic coils 301 despite theattraction between them. The attractive force between the porous magnetcomponents 302 and magnetic coils 301 is used for the purposes of themotor or generator functionality, which is enhanced over the current artbecause the gap can be made smaller due to the safety afforded by theseparation force of the pressurized fluid film 304 from the hydrostaticbearing functionality. This is because the flux field strength is verysensitive to the gap thickness. At very high pressures, this fluid filmforce may be used to counter the centrifugal force attempting toseparate the porous magnet components 302 from the rotating shaft 300.While FIG. 3 shows the use of the porous magnet components 302 as therestrictive element in the hydrostatic bearing, other well known formsof restrictive compensation such as orifice or step compensation may beemployed.

The embodiment of the hydrostatic bearing shown in FIG. 3 only providesradial restraint, so conventional rolling, plain, fluid film, ormagnetic bearings may be used for axial restraint. Preferably,additional hydrostatic bearings 303 are used to provide axial restraint,and pressurized fluid from the same labyrinth 312 and fluid source isemployed to create a hydrostatic bearing gap 308 on both ends of therotating shaft 300, creating opposing forces and providingtwo-directional axial restraint. Although not shown in the drawings, thesame bearing and motor/generator arrangement may be employed in both theaxial and radial directions.

While various methods, configurations, and features of the presentinvention have been described above and shown in the drawings, one ofordinary skill in the art will appreciate from this disclosure that anycombination of the above features can be used without departing from thescope of the present invention. It is also recognized by those skilledin the art that changes may be made to the above described methods andembodiments without departing from the broad inventive concept thereof.For example, the coils 301 shown in FIG. 3 may be located on therotating shaft 300 while the porous magnet components 302 are located onthe inner diameter of the housing 305, with electricity fed to the coils301 via a conductive contact brush. Additionally, the embodiments of theinvention are capable of being scaled up with coils and magnet diameterspotentially reaching tens of meters.

What is claimed is:
 1. A permanent magnet motor/generator comprising: ahousing; a rotating shaft supported within the housing; and ahydrostatic bearing disposed on the rotating shaft and within thehousing, the hydrostatic bearing comprising a first face that is aporous permanent magnet and a second face that is coils, wherein thehydrostatic bearing is configured to distribute a pressurized fluidacross a back surface of the porous permanent magnet, the porouspermanent magnet is configured to issue the pressurized fluid throughthe back surface to the first face, and the first face and the secondface arranged such that movement of the rotating shaft is restricted ina radial direction, whereby the permanent magnet and the coils areconfigured to generate electricity or create force.
 2. The permanentmagnet motor of claim 1, wherein the permanent magnet is porous.
 3. Thepermanent magnet motor of claim 2 1, wherein the first face and secondface are separated by a hydrostatic gap.
 4. The permanent magnet motorof claim 3, wherein the hydrostatic gap has a thickness of a pressurizedfilm created by the pressurized fluid.
 5. The permanent magnet motor ofclaim 3, wherein the pressurized fluid removes heat from bearingsurfaces of the hydrostatic bearing and from the hydrostatic gap.
 6. Thepermanent magnet motor of claim 3, wherein the pressurized fluidprovides a force in a direction opposite to a centrifugal force, whichattempts to separate the hydrostatic bearing from the rotating shaftduring rotation at high speed.
 7. The permanent magnet motor of claim 1wherein the housing further comprises a third face and a fourth facethat are permanent magnets, the third and fourth face plurality ofadditional hydrostatic bearings wherein each additional hydrostaticbearing is arranged at opposite ends of the first face such that themovement of the rotating shaft is restricted in the axial direction. 8.A method for making a permanent magnet motor or generator, the methodcomprising: providing a housing with a rotating shaft supported therein;and disposing a hydrostatic bearing on the rotating shaft and within thehousing, the hydrostatic bearing comprising a first face that is aporous permanent magnet and a second face that is coils, wherein thehydrostatic bearing is configured to distribute a pressurized fluidacross a back surface of the porous permanent magnet, the porouspermanent magnet is configured to issue the pressurized fluid throughthe back surface to the first face, and the first face and the secondface arranged such that movement of the rotating shaft is restricted ina radial direction, whereby the porous permanent magnet and the coilsare configured to generate electricity or create force.
 9. The method ofclaim 8, wherein the first face and the second face are separated by ahydrostatic gap.
 10. The method of claim 9, where the thickness of thehydrostatic gap is equal to that of a pressurized hydrostatic filmmaintained by a continuous flow of fluid pumped through the porouspermanent magnet.
 11. The method of claim 8 wherein the housing furthercomprises a third face and a fourth face that are permanent magnets, thethird and fourth face a plurality of additional hydrostatic bearings,wherein each additional hydrostatic bearing is arranged at opposite endsof the first face such that the movement of the rotating shaft isrestricted in the axial direction.
 12. A permanent magnet motor orgenerator comprising: a permanent magnet used as a restrictive elementof a hydrostatic bearing; coils, wherein the hydrostatic bearing worksdirectly between the permanent magnet and the coils and the permanentmagnet and coils are configured to generate electricity or create force.13. A permanent magnet motor or generator according to claim 12, whereinthe permanent magnet is porous and this porosity is used as therestrictive element and to issue fluid in the hydrostatic bearing.
 14. Apermanent magnet motor or generator according to claim 12, wherein ahydrostatic fluid is used as a mechanism to remove heat from therelative bearing surfaces and hydrostatic gap.
 15. A permanent magnetmotor or generator according to claim 12, wherein pressurizedhydrostatic fluid force is used to resist the centrifugal forceattempting to separate the bearing elements when there is rotation athigh speeds.
 16. A permanent magnet motor or generator according toclaim 12 wherein the permanent magnet is used as a restrictive elementin both the radial and axial directions.
 17. A permanent magnet motor orgenerator comprising: a housing; a rotating shaft supported within thehousing; and a hydrostatic bearing disposed on the rotating shaft andwithin the housing, the hydrostatic bearing comprising a first face thatis a porous permanent magnet and a second face, wherein the hydrostaticbearing is configured to distribute a pressurized fluid across a backsurface of the porous permanent magnet, the porous permanent magnet isconfigured to issue the pressurized fluid through the back surface tothe first face, and the first face and the second face arranged suchthat movement of the rotating shaft is restricted in an axial direction,whereby the first face and the second face are configured to generateelectricity or create force.
 18. The permanent magnet motor or generatorof claim 17, wherein the first face and second face are separated by ahydrostatic gap.
 19. The permanent magnet motor or generator of claim18, wherein the hydrostatic gap has a thickness of a pressurized filmcreated by the pressurized fluid.
 20. The permanent magnet motor orgenerator of claim 19, wherein the pressurized fluid removes heat frombearing surfaces of the hydrostatic bearing and from the hydrostaticgap.
 21. The permanent magnet motor or generator of claim 17, whereinthe second face is coils.
 22. A hydrostatic bearing comprising: ahousing; a rotating shaft supported within the housing; and ahydrostatic bearing disposed on the rotating shaft and within thehousing, the hydrostatic bearing comprising a first face and a secondface, wherein the hydrostatic bearing is configured to distribute apressurized fluid across a back surface of the porous permanent magnet,the first face is a porous permanent magnet configured to issue thepressurized fluid through the back surface to the first face, the firstface and the second face arranged such that movement of the rotatingshaft is restricted in either a radial or axial direction, and the firstface and the second face are separated by a hydrostatic gap created bythe pressurized fluid that issues from the first face, wherein thepressurized fluid removes heat the first face and the second face. 23.The hydrostatic bearing of claim 22 wherein the second face is coils.24. The hydrostatic bearing of claim 23 wherein the first face and thesecond face arranged such that movement of the rotating shaft isrestricted in a radial direction, whereby the permanent magnet and thecoils are configured to generate electricity or create force.